The present invention relates to a vibrator holding device disposed in, for example, a pocket pager, a portable telephone or the like and having a vibrator to soundless-inform a user about receipt of a call to the pocket pager, the portable telephone or the like with vibrations.
Hitherto, a vibrator holding device of the foregoing type has been disposed in, for example, a portable telephone as follows.
A vibrator holding device of the foregoing type has been structured such that a flexible printed circuit board is disposed in a case member of the portable telephone. Moreover, a bracket formed by sheet metal working for holding a vibration motor is attached onto the flexible printed circuit board such that the lead wire of the held vibration motor is connected to the flexible printed circuit board.
When the flexible printed circuit board is employed to reduce the size and weight of the device, the structure can easily be formed such that the metal plate bracket is attached to the upper surface of the flexible printed circuit board and the vibration motor is held by the metal plate bracket.
However, a problem arises in that generation of vibrations from the vibration motor held by the metal plate bracket results in also the flexible printed circuit board being vibrated.
To solve the above-mentioned problem, a reinforcing plate (a backing member) made of epoxy resin containing glass is bonded to the reverse side of the flexible printed circuit board. Moreover, the reinforcing plate is allowed to adhere to the case of the portable telephone with a double-coated tape. Note that a release sheet is provided on the surface of the adhesive layer of the double-coated tape in order to prevent deterioration in the adhesive force.
In a process for assembling the vibrator holding device, the metal plate bracket is attached to the upper surface of the flexible printed circuit board; the vibration motor is mounted on the metal plate bracket; and one of the release sheets is released so as to be allowed to adhere to the case so that the flexible printed circuit board is bonded and secured to the case with the double-coated tape.
However, the operation for releasing the release sheet from the double-coated tape cannot easily be automated in a trend of automating the assembling operation. Thus, the assembling operation using robots cannot be automated.
To overcome the foregoing problem, a vibrator holding device capable of reducing vibrations of the flexible printed circuit board generated by the motor without use of a double-coated tape has been disclosed in Japanese Patent Laid-Open No. 8-51286.
The vibrator holding device disclosed in Japanese Patent Laid-Open No. 8-51286 will now be described with reference to the drawings. FIG. 6 is an exploded perspective view showing a vibrator holding device disposed in a personal call receiver. FIG. 7 is a cross sectional view showing the vibrator holding device which is an essential portion of the personal call receiver.
Referring to FIG. 6, the vibrator holding device has a vibration motor 72 provided with lead wires 70 and 71 and formed into a cylindrical shape; an elastic holding member 74 into which the vibration motor 72 is press-fit to be elastically held; and a printed circuit board 77 having a fixing hole 78 for fixing a fixing portion 76 formed in the upper portion of the elastic holding member 74.
The elastic holding member 74 has a holding portion 75 into which the vibration motor 72 is press-fit so as to be held; and a slit 73 for causing the operation for press-fitting the vibration motor 72 into the holding portion 75 to be performed easily.
The printed circuit board 77 is held and located by printed-circuit-board holding ribs 81 formed in the case 79 and the cover 80. Moreover, upper and lower surfaces 85 and 86 of the elastic holding member 74 are held between inner surfaces 87 and 88 of the case 79 and the cover 80.
Therefore, the foregoing vibrator holding device, having the structure such that the vibration motor 72 is elastically held in the elastic holding member 74, is able to prevent vibration of the printed circuit board 77 attributable to vibrations generated by the vibration motor 72 without use of a double-coated tape.
The conventional vibrator holding device has the structure such that vibrations are generated when the vibration motor 72 is rotated. The vibration motor 72 generates vibrations when force acts in a radial direction with respect to the rotational shaft of the motor.
However, the foregoing vibrator holding device has the structure such that the elastic holding member 74 is held on the upper and lower surfaces 85 and 86 of the elastic holding member 74 by the inner surfaces 87 and 88 of the case 79 and the cover 80. Even if force acts in a radial direction (in a vertical direction) V and in a second radial direction (in horizontal direction) W perpendicular to the radial direction V, the force is not received by any surface, that is, no contact surface between the case 79 or the cover 80 and the elastic holding member 74 exists. Therefore, if force acts in the second radial direction W, no element exists that transmits vibrations. As a result, the body is vibrated in only one direction (in the radial direction V). In this case, the amount of vibrations is too small to inform a user of receipt of a call with the vibrations.
To enlarge the amount of vibrations, the vibration motor 72 must be rotated at high speed and the weight must be enlarged in order to farther position the center of gravity. Centrifugal force of the weight and the like results in vibrations to be transmitted to the printed circuit board 77, thus causing the electronic elements mounted on the printed circuit board 77 being broken. As a result, interference takes place between the printed circuit board 77 and an adjacent element, thus raising a first problem in that noise is generated.
The vibrator holding device has the structure such that the operation for press-fitting the vibration motor 72 into the elastic holding member 74 can smoothly be performed by providing the slit 73 for the elastic holding member 74. Since no element exists for transmitting vibrations with the force in the second radial direction, the force unintentionally acts in a direction in which the slit 73 of the elastic holding member 74 is opened when the force acts in the second radial direction W. As a result, there arises a second problem in that the vibration motor 72 is moved slightly in the elastic holding member 74 and therefore it sometimes is separated from the elastic holding member 74.
Since the vibrator holding device is accommodated in a portable telephone, a pocket pager or the like, a user unintentionally drops the portable telephone, a pocket pager or the like and thus the vibrator holding device can be broken.
If the vibrator holding device is broken, for example, the vibration motor 72 in the elastic holding member 74 must be removed from the printed circuit board 77 in order to change the vibrator holding device.
Since the elastic holding member 74 is in a state where the fixing portion 76 of the elastic holding member 74 is press-fit and engaged into the fixing hole 78 of the printed circuit board 77, engagement realized by press-fitting must be suspended carefully to prevent generation of a crack in the elastic holding member 74. Thus, there arises a third problem in that an operator must bear a heavy load and a long time is required to complete the operation.
Moreover, the foregoing vibrator holding device has a fourth problem in that, for example, an operation for soldering the lead wires 70 and 71 connected to the vibration motor 72 must be performed in a state where the printed circuit board 77 is not fixed in the case and thus the operation for soldering the lead wires 71 and 72 is too difficult.
The vibrator holding device is structured such that the conducting portions, such as a coil and a brush, and a metal cylindrical motor case for accommodating the rotational shaft of the motor, a bearing for the rotational shaft and the like are not electrically connected to each other in a case where the vibration motor 72 in each of the various wireless devices, such as a portable telephones and the pocket pagers, for transmitting/receiving electromagnetic waves is a coreless motor or a cored motor. Therefore, if the motor case absorbs electromagnetic waves, the potential of the motor case is changed. As a result, leaked electric currents are transmitted to the lead wires 70 and 71 of the vibration motor 72, thus causing the portable telephone of the lead wires 70 and 71 to be changed. Thus, there arises a fifth problem in that the vibration motor 72 encounters a problem.